End-point aware resource reservation protocol proxy

ABSTRACT

A method performed by a first network device may include receiving a request for a resource from an end-point device and acknowledging the request for the resource to the end-point device. The method may also include receiving a resource coordination message from a second network device and transmitting a return resource coordination message to the second network device.

RELATED APPLICATION

This application claims priority under 35 U.S.C. §119 based on U.S.Provisional Application No. 60/474,922, filed Jun. 3, 2003, thedisclosure of which is incorporated herein by reference.

BACKGROUND

1. Field of the Invention

Systems and methods consistent with the principles of the inventionrelate generally to network communication protocols, and moreparticularly, to a resource reservation protocol facilitated by anetwork device in a network.

2. Description of Related Art

In certain network-based applications, it may be desirable to achieve aspecified Quality of Service (QoS), that is, a guaranteed networkbandwidth and availability for such applications. To obtain thisspecified QoS, end-point devices (i.e., users of the application) mayinteract with network devices (e.g., routers, gateways, etc.) to reservesufficient resources to guarantee that the application will have thespecified QoS. Such end-point devices may be “originating” devices thatoriginate communication or “terminating” devices with whom communicationis sought.

Some network-based applications may need to perform “symmetric” resourcereservation for the applications to function properly. In suchapplications, both the originating and terminating end-point devices mayreserve resources from network devices to ensure a sufficient end-to-endQoS. Voice over Internet Protocol (VoIP) is one example of anapplication for which end-point devices need to symmetrically reserveresources (e.g., bandwidth), for example, from routing network devices.The end-point devices may coordinate this resource reservation using aResource reSerVation Protocol (RSVP), for example the RSVP specified bythe Internet Engineering Task Force (IETF).

Around the time of this symmetric resource reservation by the end-pointdevices, the associated network devices may be authorized to use, forexample, the network between the network devices. Such authorization mayuse PacketCable™-defined constructs called “gates” (and gate-relatedmessages) to control or “authorize” access by the network devices (andend-point devices) to the network on a per-flow basis. Such anarrangement, however, may result in a network device on one end (e.g.,the terminating end of the communication) allocating resources to itsend-point device without making sure that the network device on theother end (i.e., the originating end of the communication) isauthorized.

Therefore, there exists a need to better coordinate the reservation ofresources in a network.

SUMMARY

Systems and methods consistent with the principles of the inventionaddress this and other needs by terminating a resource request from anend-point device and waiting for a coordination message from a networkdevice. When the coordination message is received, the resourcesrequested by the end-point device may be committed.

In accordance with one aspect of the invention, a method may includereceiving a request for a resource and terminating the request for theresource. The method may also include receiving a resource coordinationmessage and assigning the resource identified by the request afterreceiving the resource coordination message.

In another implementation consistent with principles of the invention, amethod performed by a first network device may include receiving arequest for a resource from an end-point device and acknowledging therequest for the resource to the end-point device. The method may alsoinclude waiting for a resource coordination message from a secondnetwork device and transmitting a return resource coordination messageto the second network device. The method may further include completingthe reservation of the resource.

In a further implementation consistent with principles of the invention,a first network device may be configured to receive a first resourcereservation protocol (RSVP) message requesting that resources becommitted, transmit a second RSVP message to a sender of the first RSVPmessage, receive a third RSVP message from a second network device, andcommit the resources requested by the first RSVP message after receivingthe third RSVP message.

In yet another implementation consistent with principles of theinvention, a computer-readable medium may include instructions foracknowledging receipt of a first resource reservation protocol (RSVP)message with a first return RSVP message and instructions for delayinguntil a second RSVP message is received. The medium may also includeinstructions for sending a third RSVP message after the second RSVPmessage is received and instructions for committing one or moreresources requested by the first RSVP message after the second RSVPmessage is received.

In another implementation consistent with the principles of theinvention, a first network device is configured to receive a request toreserve resources and transmit a first resource reservation protocol(RSVP) message to a second network device requesting that firstresources be committed. The first network device is further configuredto receive a second RSVP message from the second network devicerequesting that second resources be committed, commit the secondresources based on receipt of the second RSVP message, receive a thirdRSVP message from the second network device indicating that the firstresources were committed, and acknowledge reservation of the requestedresources.

In a further implementation consistent with the principles of theinvention, a first network device is configured to receive a messagethat instructs the first network device whether to act as an originatingnetwork device or a terminating network device, and exchange resourcereservation protocol (RSVP) messages with a second network device toreserve resources for a communication between a first device associatedwith the first network device and a second device associated with thesecond network device.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate embodiments of the invention and,together with the description, explain the invention. In the drawings,

FIG. 1 is a diagram illustrating an exemplary system in which conceptsconsistent with aspects of the invention may be implemented;

FIG. 2 is an exemplary signaling diagram of the system of FIG. 1according to an implementation consistent with the principles of theinvention;

FIGS. 3A and 3B are exemplary messaging processes consistent with theprinciples of the invention;

FIG. 4 is a diagram illustrating an exemplary generalized system inwhich concepts consistent with aspects of the invention may beimplemented;

FIG. 5 is an exemplary generalized signaling diagram of the generalizedsystem of FIG. 4 according to an implementation consistent with theprinciples of the invention; and

FIG. 6 is an exemplary generalized messaging process consistent with theprinciples of the invention.

DETAILED DESCRIPTION

The following detailed description of the invention refers to theaccompanying drawings. The same reference numbers may be used indifferent drawings to identify the same or similar elements. Also, thefollowing detailed description does not limit the invention. Instead,the scope of the invention is defined by the appended claims andequivalents.

Systems and methods consistent with the principles of the invention mayperform improved RSVP signaling. For example, such systems and methodsmay terminate a resource request from an end-point device and wait for acoordination message from a network device. When the coordinationmessage is received, the resources requested by the end-point device maybe committed.

Exemplary System

FIG. 1 is a diagram illustrating an exemplary system 100 in whichconcepts consistent with aspects of the invention may be implemented.System 100 may include a multimedia terminal adapter (MTA) 110, a cablemodem termination system (CMTS) 120, a call management server (CMS) 130,a CMS 140, a CMTS 150, and an MTA 160. MTAs 110/160 may be respectivelyconnected to CMTSs 120/150 by radio frequency (RF) links 115/155, suchas those found in a cable modem network. CMTSs 120/150 may berespectively connected to CMSs 130/160 by links 125/145 that supportInternet Protocol (IP) communication. CMS 130 may be connected to CMS140 by a backbone 135, such as a portion of a public switched telephonenetwork (PSTN) or other backbone network.

For the discussion to follow, system 100 will be described with respectto a VoIP application performed over system 100. Although system 100 maybe used to facilitate other applications, VoIP is one example of anapplication that entails symmetric resource reservation. For thepurposes of discussion, a telephone device 105 (e.g., a conventionaltelephone or an IP-based telephone) connected to MTA 110 will be assumedto originate a telephone call that will terminate with a telephonedevice 165 connected to MTA 160. Hence, MTA 110, CMTS 120, and CMS 130may all be referred to as “originating” devices, and CMS 140, CMTS 150,and MTA 160 may all be referred to as “terminating” devices. Thestructure and operation of typical MTA, CMTS, and CMS devices will beunderstood by those skilled in the communication arts, and only thosedeviations from such typical devices will be described.

MTA 110 is the originating end-point device of system 100. Although notshown, MTA 110 may include, or be connected to, a cable modem (CM)configured to communicate with CMTS 120 under one of the Data over CableService Interface Specifications (DOCSIS) (e.g., DOCSIS 1.1 or DOCSIS2.0). MTA 110 may function to communicate information between theconnected telephone device 105 and CMTS 120. MTA 110 may also attempt toreserve resources (e.g., bandwidth) from CMTS 120 for the call fromconnected telephone device 105.

CMTS 120 may be configured to facilitate communication between MTA 110and CMS 130. CMTS 120 may be configured to allocate resources (e.g.,bandwidth) to MTA 110. CMTS 120 may also be configured to receive gateauthorization from CMS 130.

CMS 130 may be configured to set up calls for MTA 110. For example, CMS130 may be configured to communicate with MTA 110 to set up calls,arrange gate authorization for CMTS 120, and arrange for resources onbackbone 135.

MTA 160, CMTS 150, and CMS 140 may be similarly configured to MTA 110,CMTS 120, and CMS 130, respectively. The structure and operation ofthese devices will not be repeated for this reason.

Exemplary Signaling Diagram

FIG. 2 is an exemplary signaling diagram 200 of system 100 according toone implementation consistent with the principles of the invention.Certain signals may not be labeled with reference numbers, for ease ofexplanation. These unlabeled signals are typically acknowledgments ofearlier signals, and may not merit individual discussion. A morecomprehensively described signaling scheme (including RSVP signaling)that may be employed in system 100 appears in the PacketCable™ DynamicQuality-of-Service specification (PKT-SP-DQOS-I05-021127), 5th release,Nov. 27, 2002, which is incorporated by reference herein.

MTA 110 may begin by sending a notify (NTFY) message 205 to CMS 130 toindicate digits pressed to originate a call. CMS 130 may respond with acreate connection (CRCX) message 210. In response to signalinginformation from MTA 110, CMS 130 may send a gate allocation(Gate-Alloc) message 215 to CMTS 120 to check the current resource(e.g., number of call allocations requested) consumption of MTA 110 byconsulting CMTS 120. Upon response from CMTS 120, originating CMS 130may send an invite message to terminating CMS 140.

CMS 140 may send CMTS 150 a gate setting (Gate-Set) message 220 toauthorize CMTS 150 to admit the new call connection. A Gate-Set message,such as Gate-Set message 220, may instruct a CMTS to act as either anoriginating CMTS or a terminating CMTS. In this case, Gate-Set message220 may instruct CMTS 150 to act as a terminating CMTS. In anotherimplementation, another type of message (other than a Gate-Set message)may be used to instruct a CMTS as to whether to act as an originatingCMTS or a terminating CMTS. The alternative messaging may even includean object within an RSVP_PATH message, such as RSVP_PATH message 250 fororigination assignment and RSVP_PATH message 230 for terminationassignment.

After acknowledgment from CMTS 150, CMS 140 may send terminating MTA 160a CRCX message 225 to create a connection. At this point, MTA 160 mayattempt to reserve resources (e.g., bandwidth) from CMTS 150 for theupcoming call by sending an RSVP_PATH message 230 to CMTS 150. CMTS 150may immediately send a return RSVP_RESV message 235 to MTA 160. Receiptof RSVP_RESV message 235 by MTA 160 indicates to MTA 160 that therequested resources have been successfully reserved. In oneimplementation consistent with the principles of the invention, CMTS 150does not, however, actually reserve the requested resources end-to-end,but instead only reserves the local resources between the MTA 160 andCMTS 150 when it sends RSVP_RESV message 235 to MTA 160.

Such a reply to MTA 160 with RSVP_RESV message 235 may have thefollowing implications. MTA 160 may, upon receipt of RSVP_RESV message235, assume that CMTS 150 has coordinated resource reservations withCMTS 120, when CMTS 150 has not in fact performed such coordination.From the perspective of MTA 160, the signaling is proceeding regularly.By immediately returning RSVP_RESV message 235, but not committingresources, CMTS 150 avoids the potential problem of committing resourcesbefore it is sure that CMTS 120 is authorized by CMS 130 (e.g., via gatesetting message 240) for the call connection.

After an acknowledgment from MTA 160, CMS 130 may send CMTS 120 aGate-Set message 240 to authorize CMTS 120 to admit the new callconnection. As described above, Gate-Set message 240 (or another type ofmessage) may instruct CMTS 120 to act as either an originating CMTS or aterminating CMTS. In this case, Gate-Set message 240 may instruct CMTS120 to act as an originating CMTS. CMS 130 may then send MTA 110 a MDCXmessage that instructs the MTA to modify its connection and reserve theend-to-end resources.

MTA 110 may then seek to reserve sufficient resources for the call bysending CMTS 120 an RSVP_PATH message 250. CMTS 120 may attempt tocoordinate this resource reservation with CMTS 150 by sending anRSVP_PATH message 255. Upon receiving RSVP_PATH message 255, CMTS 150may reserve the resources that it did not reserve when requested by MTA160 via RSVP_PATH message 230. CMTS 150 may reserve the resources thatwere requested earlier by MTA 160 at this time, because receipt ofRSVP_PATH message 255 from CMTS 120 implies that CMTS 120 is authorizedby CMS 130 for the call connection.

CMTS 150, instead of immediately sending an RSVP_RESV message to CMTS120, may start to reserve resources in the reverse direction by sendingRSVP_PATH message 260 to CMTS 120. Upon receipt of RSVP_PATH message260, CMTS 120 may reserve the resources that were requested, and confirmthe reservation of the resources in the reverse path using RSVP_RESVmessage 265. Upon receipt of RSVP_RESV message 265, CMTS 150 replies tothe earlier received RSVP_PATH message 260 confirming that the resourcesare reserved, and starts the resources reservation of the path viaRSVP_RESV message 270 to CMTS 120. This RSVP_RESV message 270 completesthe “handshake” between CMTS 120 and CMTS 150 that coordinates symmetricresource reservation for the call between MTA 110 and MTA 160. Aroundthis time, CMTS 120 may send a return RSVP_RESV message 275 to MTA 110to indicate that the end-to-end resources requested by RSVP_PATH message250 have been successfully reserved.

Subsequent signaling associated with a call between MTA 110 and MTA 160(or more precisely between associated telephone devices 105 and 165) insystem 100 may be described in the PacketCable™ DynamicQuality-of-Service specification (PKT-SP-DQOS-I05-021127), 5th release,Nov. 27, 2002, which is incorporated by reference herein. Because it maybe performed in a typical manner, such subsequent signaling will not beexplicitly described herein.

Exemplary Protocol Process

FIGS. 3A and 3B are exemplary RSVP processes which may vary depending onwhether the CMTS is a terminating one or originating one. FIG. 3Aillustrates RSVP processing in the case of a terminating CMTS. FIG. 3Billustrates RSVP processing in the case of an originating CMTS.

The RSVP processing of FIG. 3A may be performed by a termination networkdevice, such as terminating CMTS 150. Terminating CMTS 150 may performother actions in setting up an application session (e.g., a VoIP call),but the processing of FIG. 3A concentrates on the RSVP portion of suchsignaling.

In FIG. 3A, processing may begin by receiving a local resourcereservation request [act 310]. In one implementation consistent with theprinciples of the invention, terminating CMTS 150 may receive anRSVP_PATH message 230 from terminating MTA 160. Processing may continueby terminating the local resource reservation request andassigning/committing local resources, but not assigning/committing therequested end-to-end resources [act 320]. Terminating CMTS 150, forexample, may send return RSVP_RESV message 235 to MTA 160. TerminatingCMTS 150 may not, at this time, commit the end-to-end resourcesrequested by MTA 160 in the resource reservation request (e.g.,RSVP_PATH message 230). Instead, terminating CMTS 150 may wait until itreceives a resource coordination message from an originating networkdevice before committing the requested resources.

Processing may continue by receiving such a resource coordinationmessage from an originating network device, such as CMTS 120 [act 330].For example, terminating CMTS 150 may receive RSVP_PATH message 255 fromoriginating CMTS 120.

Instead of completing the resource reservation that is initiated by theoriginating network device, terminating CMTS 150 starts resourcereservation in the reverse direction [act 340]. Upon completion of theresource reservation in the reverse direction, terminating CMTS 150completes the resource reservation that the originating network devicestarted [act 350].

The RSVP processing of FIG. 3B may be performed by an originatingnetwork device, such as originating CMTS 120. Originating CMTS 120 mayperform other actions in setting up an application session (e.g., a VoIPcall), but the processing of FIG. 3B concentrates on the RSVP portion ofsuch signaling.

In FIG. 3B, processing may begin by receiving a local resourcereservation request [act 370]. In one implementation consistent with theprinciples of the invention, originating CMTS 120 may receive anRSVP_PATH message 250 from originating MTA 110. Processing may continueby initiating an RSVP_PATH message 255 to reserve the resources [act375].

Upon receipt of the reverse direction RSVP_PATH message 260, originatingCMTS 120 may complete the resource reservation of the reverse directionby initiating RSVP_RESV message 265 [act 380]. Upon completion of theresource reservation by originating CMTS 120, which was started by thereception of RSVP_RESV message 270, originating CMTS 120 may completethe local reservation via RSVP_RESV message 275 to originating MTA 110.

Exemplary Generalized System

Systems and methods consistent with the principles of the invention arenot limited to a VoIP application over a cable modem system, asillustrated in FIG. 1. Rather, systems and methods consistent with theprinciples of the invention are applicable to any system/method thatneeds end-to-end QoS, and more generally, to any application and systemin which bi-directional resources should be synchronously reserved bynetwork devices, such as routers.

FIG. 4 is a diagram illustrating an exemplary generalized system 400 inwhich concepts consistent with aspects of the invention may beimplemented. System 400 may include an end-point device (EPD) A 410, anetwork device (ND) A 420, a ND B 430, and an EPD B 440. Although notshown in FIG. 4, NDs 420 and 430 may communicate over a network, andsuch network communication by NDs 420 and 430 may becoordinated/controlled by one or more coordinating devices (e.g.,controllers).

EPDs 410 and 440 may be configured to request resources from respectiveNDs 420 and 430 using an RSVP protocol. EPDs 410 and 440 also may beconfigured to communicate after being assigned such resources. It shouldbe noted, however, that the application in which EPDs 410 and 440communicate need not be VoIP. Communication between EPDs 410 and 440 mayinvolve other protocols, such as the hypertext transfer protocol (HTTP)or the H.323 ITU-T recommendation. EPDs 410 and 440 may, but need not,be MTAs; they may also be other network communication devices that areP2P (peer-to-peer) applications, such as gaming applications, videoconferencing applications, etc.

NDs 420 and 430 may be configured to assign/commit resources to EPDs 410and 440, and coordinate between themselves to symmetricallyassign/commit such resources. NDs 420 and 430 may be network devices,such as switches or routers. Although arranged similar to CMTSs 120 and150, either one of NDs 420 and 430 may be on, for example, theterminating side of a network communication session.

Exemplary Generalized Signaling Diagram

FIG. 5 is an exemplary generalized signaling diagram of generalizedsystem 400 according to an implementation consistent with the principlesof invention. Although system 400 may perform othercommunication/signaling, only a certain portion of an RSVP signalingexchange is illustrated in FIG. 5 for clarity of explanation withrespect to generalized system 400.

EPD 440 may attempt to reserve resources from ND 430 for a communicationwith EPD 410 by sending an RSVP_PATH message 510 to ND 430. ND 430 mayterminate the resource request by sending a return RSVP_RESV message 520to EPD 440. Receipt of RSVP_RESV message 520 by EPD 440 may indicate toEPD 440 that the requested resources have been successfully reserved.

In one implementation consistent with the principles of the invention,ND 430 does not, in fact, reserve the requested resources when it sendsRSVP_RESV message 520 to EPD 440. Rather, ND 430 waits for acoordinating RSVP_PATH message 530 from ND 420. Upon receiving RSVP_PATHmessage 530, ND 430 may assign/commit the resources that it did not whenrequested by EPD 440 via RSVP_PATH message 510.

ND 430 may send a coordinated RSVP_PATH message 535 to ND 420. Thus, ND430 may wait/delay until it receives RSVP_RESV message 540 from ND 420to send its RSVP_RESV message 550 to communicate the reverse directionresource reservation completion from its end (terminating) of system400.

The reception of RSVP_RESV message 550 indicates the completion ofbi-directional resource reservation to ND 420. Upon receiving RSVP_RESVmessage 550, ND 420 may reserve any resources previously requested byEPD 410. ND 420 may confirm reservation of its resources for the call bysending a return RSVP_RESV message (not shown) to ND 430 that completesthe RSVP “handshake” between ND 420 and ND 430.

Exemplary Generalized Protocol Process

FIG. 6 is an exemplary generalized RSVP process 600 consistent with theprinciples of the invention. Process 600 may be performed by one networkdevice, such as ND 430. It should be noted that the performing networkdevice (e.g., ND 430) may be an originating ND or a terminating ND inthe context of a particular communication. ND 430 may perform otheractions in the communication, but process 600 concentrates on the RSVPportion of such signaling.

Process 600 may begin by receiving a resource reservation request froman end-point device [act 610]. In one implementation consistent with theprinciples of the invention, ND 430 may receive RSVP_PATH message 510from EPD 440. Processing may continue by terminating the resourcereservation request and assigning/committing local resources, but notassigning/committing the requested end-to-end resources [act 620]. ND430, for example, may send return RSVP_RESV message 520 to EPD 440.

ND 430 may wait until it receives a resource coordination message fromanother network device [act 630] before committing the requestedresources. For example, ND 430 may receive RSVP_PATH message 530 from ND420. ND 430 may assign the resources requested by EPD 440 around thistime.

Processing may continue by acknowledging the resource coordinationmessage [act 640]. For example, ND 430 may send RSVP_RESV message 540 toND 420. Process 600 may continue by sending a resource coordinationmessage to the other network device [act 650]. For example, ND 430 maysend RSVP_PATH message 550 to ND 420.

Although not part of process 600 that is performed by ND 430, ND 420 mayassign requested resources to EPD 410 upon receiving RSVP_PATH message550 from ND 430. This (in conjunction with a return RSVP_RESV message(not shown) from ND 420) may conclude the coordination of symmetricresource allocation between ND 420 and ND 430.

CONCLUSION

Consistent with the principles of the present invention, a networkdevice may perform improved RSVP signaling. For example, a networkdevice may terminate a resource request from an end-point device andwait until a coordination message from another network device. When thecoordination message is received, the resources requested by theend-point device may be committed. The network device may alsoacknowledge the coordination message and send a coordination message ofits own.

The foregoing description of embodiments of the present inventionprovides illustration and description, but is not intended to beexhaustive or to limit the invention to the precise form disclosed.Modifications and variations are possible in light of the aboveteachings or may be acquired from practice of the invention.

For example, although the above-described RSVP terminating and delayingscheme has been described with respect to a terminating network device,such as CMTS 150, such a scheme also may be performed by an originatingnetwork device (e.g., CMTS 120).

While series of acts have been described with respect to FIGS. 3A, 3B,and 6, the order of the acts may vary in other implementationsconsistent with the present invention. Also, non-dependent acts may beperformed in parallel. Further, the acts in these figures may beimplemented as instructions, or groups of instructions, in acomputer-readable medium, such as an optical, magnetic, solid-state,integrated circuit, or other type of typical medium read by processors.For example, CMTS 150 and/or ND 430 may include a processor (not shown)configured to execute such instructions on the computer-readable mediumto perform the acts in FIGS. 3A, 3B, and 6.

No element, act, or instruction used in the description of the presentapplication should be construed as critical or essential to theinvention unless explicitly described as such. Also, as used herein, thearticle “a” is intended to include one or more items. Where only oneitem is intended, the term “one” or similar language is used. Further,the phrase “based on” is intended to mean “based, at least in part, on”unless explicitly stated otherwise. The scope of the invention isdefined by the claims and their equivalents.

1. A first network device, comprising: means for receiving a firstresource reservation protocol (RSVP) message requesting that resourcesbe committed for a communication between devices; means for transmittinga second RSVP message to a sender of the first RSVP message in responseto receiving the first RSVP message; means for receiving, from a secondnetwork device, a third RSVP message to reserve resources for thecommunication in a first direction, the second network device beingdifferent than the sender of the first RSVP message; and means fortransmitting, to the second network device, a fourth RSVP message toreserve resources in a second direction, opposite the first direction,for the communication.
 2. The first network device of claim 1, where thesender of the first RSVP message is an end-point device.
 3. A firstnetwork device to: receive a request to reserve resources for acommunication between devices; transmit a first resource reservationprotocol (RSVP) message to a second network device requesting that firstresources be committed for the communication; receive a second RSVPmessage from the second network device requesting that second, differentresources be committed for the communication; commit the secondresources based on receipt of the second RSVP message; receive a thirdRSVP message from the second network device indicating that the firstresources were committed; and acknowledge reservation of the requestedresources.
 4. The first network device of claim 3, where the first RSVPmessage and the third RSVP message are RSVP_PATH messages, and where thesecond RSVP message is an RSVP_RESV message.
 5. The first network deviceof claim 3, where the first network device is further to receive amessage that informs the first network device whether to function as anoriginating network device or a terminating network device.
 6. A firstnetwork device, comprising: means for receiving a request to reserveresources for a communication between devices; means for transmitting afirst resource reservation protocol (RSVP) message to a second networkdevice requesting that first resources be committed for thecommunication; means for receiving a second RSVP message from the secondnetwork device requesting that second, different resources be committedfor the communication; means for committing the second resources basedon receipt of the second RSVP message; means for receiving a third RSVPmessage from the second network device indicating that the firstresources were committed; and means for acknowledge reservation of therequested resources.
 7. The first network device of claim 6, further tocomprising: means for transmitting fourth and fifth RSVP messages to thesecond network device after receiving the third RSVP message from thesecond network device.
 8. The first network device of claim 7, where thefourth RSVP message is an RSVP_PATH message and the fifth RSVP messageis an RSVP_RESV message.
 9. A first network device to: receive a firstresource reservation protocol (RSVP) message requesting that resourcesbe committed for a communication between devices; transmit a second RSVPmessage to a sender of the first RSVP message in response to receivingthe first RSVP message; receive, from a second network device, a thirdRSVP message to reserve resources for the communication in a firstdirection, the second network device being different than the sender ofthe first RSVP message; and transmit, to the second network device, afourth RSVP message to reserve resources in a second direction, oppositethe first direction, for the communication.
 10. The method of claim 9,where a particular one of the devices includes a multimedia terminaladapter, and where the resources include sufficient bandwidth for avoice over internet protocol (VoIP) session.
 11. The first networkdevice of claim 9, where the first network device is a router.
 12. Amethod performed by a first network device, the method comprising:receiving, by the first network device, a first resource reservationprotocol (RSVP) message requesting that resources be committed for acommunication between devices; transmitting, by the first networkdevice, a second RSVP message to a sender of the first RSVP message inresponse to receiving the first RSVP message; receiving, by the firstnetwork device and from a second network device, a third RSVP message toreserve resources for the communication in a first direction, the secondnetwork device being different than the sender of the first RSVPmessage; and transmitting, by the first network device and to the secondnetwork device, a fourth RSVP message to reserve resources in a seconddirection, opposite the first direction, for the communication.
 13. Themethod of claim 12, where the first network device is a cable modemtermination system.
 14. A method performed by a first network device,the method comprising: receiving a request to reserve resources for acommunication between devices; transmitting a first resource reservationprotocol (RSVP) message to a second network device requesting that firstresources be committed for the communication; receiving a second RSVPmessage from the second network device requesting that second, differentresources be committed for the communication; committing the secondresources based on receipt of the second RSVP message; receiving a thirdRSVP message from the second network device indicating that the firstresources were committed; and acknowledging reservation of the requestedresources.
 15. The method of claim 14, further comprising: receiving amessage that identifies whether the first network device is to functionas an originating network device or a terminating network device. 16.The first network device of claim 14, where the sender of the first RSVPmessage is a multimedia terminal adapter.
 17. A computer-readable mediumstoring executable instructions that, when executed by a processor of afirst network device, cause the processor to: receive a first resourcereservation protocol (RSVP) message requesting that resources becommitted for a communication between devices; transmit a second RSVPmessage to a sender of the first RSVP message in response to receivingthe first RSVP message; receive, from a second network device, a thirdRSVP message to reserve resources for the communication in a firstdirection, the second network device being different than the sender ofthe first RSVP message; and transmit, to the second network device, afourth RSVP message to reserve resources in a second direction, oppositethe first direction, for the communication.